Steam generators



United States Patent US. Cl. 122-235 Claims ABSTRACT OF THE DISCLOSURE A radiant heat exchanger positioned in the upper region of the furnace of a steam generator and comprised of a curtain or panel of vertically aligned tubes extending horizontally across the furnace toward the front wall of the furnace. At a location adjacent this front wall these tubes are bent to form a panel extending parallel with this wall and upwardly of the wall with the tubes projecting through the roof of the furnace where they are connected with an outlet header. The other ends of the tubes are connected with a vertical header adjacent the rear wall of the furnace.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to steam generators and has reference to the provision in such generators of radiant superheaters in the upper part of the furnace of the steam generators.

In those generators in which radiant heating surface is required to obtain a required degree of superheat, or to secure a required load of steam temperature characteristic, it is often convenient for this surface to be installed in the form of widely spaced, multiflow tube elements or curtains positioned horizontally at the point of exit of gases from the combustion chamber of the furnace. Such a position enables the surface to be easily supported in a zone of high heat absorption, and, in addition, the position is such that the tube elements can be used to counteract any tendency to unbalanced flow of combustion products.

To secure a requisite characteristic and performance, it may be necessary to provide additional radiant superheating surface and this can be done by locating tube elements in the front wall of the furnace. However, such an arrangement has, in the past, involved the use of separate headers between the curtains and the front wall superheater. This involves extra pipework and expause and in addition, the distribution of steam is prejudiced by the presence of the intermediate headers.

According to the present invention, a steam generator includes a first radiant superheating surface positioned at or adjacent the point of exit of combustion products from that furnace, which surface is extended within the furnace to provide, on the wall of the latter, a second radiant superheating surface.

The first superheating surface may be supported by sling tubes which depend from the roof of the furnace and assist in maintaining the alignment of that surface.

Both surfaces normally consist of a plurality of tubes interconnected between inlet and outlet headers.

In one embodiment of the invention the first surface may consist of a curtain of substantially coplanar flow tubes. From these tubes additional tubes extend and make up the second surface. More than one such curtain may be used, the tubes of the additional curtains lying in planes spaced laterally from but parallel to that of the tubes of the first-mentioned curtain. The tubes of the first curtain may be looped to provide a greater radiant surface and looping may also be used to increase the extent of the second radiant surface.

Where sling tubes are employed, these and the tubes of the first superheating surface to which they are connected may form part of another and independent circuit either steam or water.

Supply and exhaust of fluid to and from the surface is via headers located outside the furnace in the known manner.

DESCRIPTION OF THE DRAWINGS By way of example only, embodiments of the invention will now be described in greater detail with reference to the accompanying drawings of which:

FIG. 1 is in the nature of a fragmentary vertical section and shows in schematic form only part of a first embodiment;

FIG. 2 is a section on the line IIII of FIG. 1;

FIG. 3 is a view similar to FIG. 1 and shows in schematic form only part of a second embodiment;

FIG. 4 is a section on the line IV-IV of FIG. 3;

FIG. 5 is a view similar to FIG. 1 and shows in schematic form only part of a third embodiment; and

FIG. 6 is a section on the line VIVI of FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 shows in schematic form only part of the upper portion of the furnace of a steam generator, the walls of the furnace being indicated by lines 1, 2 but which, in practice, are panels of water tubes. Combustion products from fuel burners (not shown) pass upwardly through the furnace which they leave via a gas pass indicated at 3. At first radiant superheating surface is provided in the form of a curtain 4 located adjacent the gas pass 3 and consists of a substantially coplanar assembly of steam tubes connected at one end to an inlet header 5 and extending across the furnace to that wall thereof indicated by line 1. This wall 1 is the front wall of the furnace opposite the outlet 3 with the transverse configuration of the furnace being generally rectangular. The vertically extending inlet header 5 is disclosed located in the nose bafile of the furnace and is in alignment with the vertically aligned tubes that form the curtain 4. The majority of the tubes of the curtain 4 are extended to form a second superheating surface adjacent the wall 1 and shown in FIGS. 1 and 2 at 6. The second superheating surface or curtain 6 is normal to the curtain 4 and, accordingly, the tubes that make up the curtain 4 must be bent from the plane of this curtain in order to form the curtain 6. FIGURE 2 discloses how these tubes are bent in order to form this second superheating surface or curtain adjacent the front furnace wall 1.

To provide support for the curtain 4 and to help maintain the alignment of the latter, two pairs of sling tubes 7 and 8 are provided. The tubes of each pair are supported at their upper end and pass downwardly from the furnace roof one on each side of the curtain 4. The tubes of the pair 7 of sling tubes are connected to the lowermost pair of tubes of the curtain while the tubes of the pair 8 are connected to the next to lowermost pair of tubes of the curtain 4. The particular configuration adopted assists in maintaining alignment of the individual tubes in addition to supporting the complete curtain 4 from the roof of the furnace or the steel work normally present above the roof.

The sling tubes as they extend through the roof and down to the curtain 4 are in vertical alignment with the curtain. At the curtain the tubes are bent so that they effectively embrace the curtain with one tube on each side of the curtain, extending the vertical extent of the curtain and are then bent beneath the curtain so as to again be in alignment with the curtain.

The sling tubes from the curtain 4 are thus set both horizontally and vertically and connect intermediate a common inlet header 5 and common outlet header 9 to which the tubes of curtain 4 and superheating surface 6, respectively, are also connected.

Thus it will be appreciated that the two superheating surfaces provided in the embodiment of FIG. 1 are directly connected internally and use common headers 5 and 9. The sling tubes are readily drainable. In addition, the absence of intermediate headers encourages steam distribution, there being a bigger pressure drop between the headers 5 and 9. Reductions in cost are secured by the omission of the intermediate headers and their associated pipework.

The curtain 4 may have two loops or more in order to provide a required steam flow in each tube of the curtain. Also, a plurality of curtains may be used and FIG. 4 shows such an arrangement. Curtains 13, 14 and 15 extend across the combustion chamber from inlet headers of which only one header 5 is shown, each curtain has loops 16 and 17. The tubes of the curtains are supported by spaced pairs of sling tubes of which only the pairs 18, 19 supporting curtain 13 are shown. The sling tubes are connected in a manner similar to that described above with reference to the embodiment shown in FIGS. 1 and 2 While the majority of the tubes of the curtains are extended to form second radiant superheating surfaces 20 adjacent the wall 1. The surfaces 20 penetrate the roof of the furnace and are joined to a common outlet header 21 to which the sling tubes may also be connected.

It may be found that the tubes adjacent the boiler wall do not provide adequate heating surface and an increase in surface can be obtained by looping these tubes. FIG. 6 shows one particular way of achieving the extra surface in which the tubes of a second radiant superheating surface 22 adjacent the wall 1 are looped as indicated at 23. In addition, these tubes are taken through the furnace roof and then returned through the roof and looped inside the furnace as at 24, the loop being located between the pairs of sling tubes 25, 26. FIG. 5 also shows the use of a curtain 27 having loops 28, 29. Preferably, the pitch across the furnace of loops, such as loop 24, is, for example, one third or one half of that of the tubes of the curtain 27 so that the sling tubes will be coplanar with the tubes of the loop 24.

It is not essential to take the tubes of the surface 22 through the roof and then return them. As an alternative, the tubes may be taken along the roof as indicated at 11 in FIG. 1 and then looped into the combustion chamber.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such i merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall Within the purview of my invention.

What I claim is:

1. In a steam generator an upright furnace having a lateral gas outlet at its upper end, the improvement comprising radiant heating surface in the upper furnace region comprising a curtain of vertically aligned tubes extending laterally across the furnace toward the Wall opposite said outlet, said tubes being bent adjacent said wall and Within the furnace to form a vertically extending curtain parallel with said wall and extending up out of the roof of the furnace, inlet and outlet headers between which said tubes are connected.

2. The steam generator of claim 1 wherein said curtain parallel with said wall is bent at the upper end of the furnace to extend along the inner side of the roof a distance and then vertically up through the roof.

3. The steam generator of claim 1 wherein the inlet header is vertically disposed adjacent thecurtain of vertically aligned tubes and the outlet header is horizontally disposed above the furnace.

4. The steam generator of claim 1 wherein support is provided by a pair of the tubes being bent to extend upward and above the curtain formed by the vertically aligned tubes.

5. The steam generator of claim 1 wherein there are a plurality of curtains spaced across the furnace.

6. The steam generator of claim 1 wherein said vertically extending curtain has the tubes thereof bent and disposed to form still another curtain extending down into the furnace and generally normal to the wall opposite said outlet.

7. The steam generator of claim 1 wherein said vertically extending curtain has the tubes thereof bent and disposed to form a plurality of additional curtains extending down into the furnace and generally normal to the wall opposite said outlet and with each of this additional curtain being made up of only a portion of the tubes in said vertically extending curtain.

8. The steam generator of claim 6 including a pair of sling tubes extending adjacent the lateral ends of said other curtain and supporting the curtain of vertically aligned tubes extending across the furnace.

9. The steam generator of claim 8 wherein the firstmentioned curtain is comprised of a plurality of vertically aligned tubes that extend back and forth across the furnace to form a plurality of loops.

1%. The steam generator of claim 1 wherein the vertically extending curtain is comprised of tubes that are looped to extend vertically up and down the curtain a plurality of times.

References Cited UNITED STATES PATENTS 3,213,831 10/1965 Hochmuth l2224() X 3,307,523 3/1967 Palchik et al. 1225l0 X FOREIGN PATENTS 917,731 9/1954 Germany.

OTHER REFERENCES Fischer, German Application No. 1,174,328, published July 23, 1964.

CHARLES I. MYHRE, Primary Examiner U.S. Cl. X.R. 122476 

